World Soil-Type Maps, Food and Agriculture Organization of the United Nations
World Reference Base for Soil Resources Map (Polar Projection, 1999). Soil-type map with definitions.
Harmonized World Soil Database Map (Mollweide Projection, 2007). Soil-type map with key.
Harmonized World Soil Database Map (2010) is a very slow interactive high resolution soil-type map or soil-type map with key.
Global Soil Information, PLOS ONE, 9(8) e105992 (2014) or World Soil pH (0-5 cm).
Regional Soil Maps
US Midwest CEC (jpg) from USDA National Agroforestry Center
US Soil pH (png) from Soil Types (2008), Biota of North America Program (BONAP)
Africa CEC and pH (png) from International Soil Reference and Information Centre (ISRIC)
European Soil Properties Maps (png or pdf) from Soil Atlas of Europe (2005), European Soil Data Centre (ESDAC)
Soil of Europe Map with key (png) from Soil Atlas of Europe (2005), European Soil Data Centre (ESDAC)
Europe Base Saturation Map (pdf) from Forestry Department (2011), United Nations Economic Commission for Europe (UNECE)
China CEC Map (png) and pH Map (png) by depth from "A China data set of soil properties", JAMES, 5, 212-224 (2013)
Global Assessment of Terrestrial Ecosystem Sensitivity to Acidic Deposition, Stockholm Environment Institute
World sensitivity map copy (2002)
Appendix I has CEC and Base Saturation values for soil types copy (1998)
Agricultural Problem Soils from FAO ProSoil (2000). See especially
Acid soils, Podzols, Acrisols and Ferralsols
Chemical soil parameters, as used by the Harmonized World Soil Database (2012).
Chemical properties, as used by the United Nations Food and Agriculture Organization (FAO).
Soils | What Happens to Acid Rain? | ChemConnections
Links verified 3/16/2018.